[PATCH 15/33] efi/gop: Allow specifying mode number on command line

Ard Biesheuvel
2020-04-24T13:06:50Z

From: Arvind Sankar <nivedita@alum.mit.edu>

Add the ability to choose a video mode for the selected gop by using a
command-line argument of the form
video=efifb:mode=<n>

Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Link: https://lore.kernel.org/r/20200320020028.1936003-12-nivedita@alum.mit.edu
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
Documentation/fb/efifb.rst | 20 +++-
.../firmware/efi/libstub/efi-stub-helper.c | 3 +
drivers/firmware/efi/libstub/efistub.h | 2 +
drivers/firmware/efi/libstub/gop.c | 107 ++++++++++++++++++
4 files changed, 129 insertions(+), 3 deletions(-)

diff --git a/Documentation/fb/efifb.rst b/Documentation/fb/efifb.rst
index 04840331a00e..367fbda2f4da 100644
--- a/Documentation/fb/efifb.rst
+++ b/Documentation/fb/efifb.rst
@@ -2,8 +2,10 @@
What is efifb?
==============

-This is a generic EFI platform driver for Intel based Apple computers.
-efifb is only for EFI booted Intel Macs.
+This is a generic EFI platform driver for systems with UEFI firmware. The
+system must be booted via the EFI stub for this to be usable. efifb supports
+both firmware with Graphics Output Protocol (GOP) displays as well as older
+systems with only Universal Graphics Adapter (UGA) displays.

Supported Hardware
==================
@@ -12,11 +14,14 @@ Supported Hardware
- Macbook
- Macbook Pro 15"/17"
- MacMini
+- ARM/ARM64/X86 systems with UEFI firmware

How to use it?
==============

-efifb does not have any kind of autodetection of your machine.
+For UGA displays, efifb does not have any kind of autodetection of your
+machine.
+
You have to add the following kernel parameters in your elilo.conf::

Macbook :
@@ -28,6 +33,9 @@ You have to add the following kernel parameters in your elilo.conf::
Macbook Pro 17", iMac 20" :
video=efifb:i20

+For GOP displays, efifb can autodetect the display's resolution and framebuffer
+address, so these should work out of the box without any special parameters.
+
Accepted options:

======= ===========================================================
@@ -36,4 +44,10 @@ nowc Don't map the framebuffer write combined. This can be used
when large amounts of console data are written.
======= ===========================================================

+Options for GOP displays:
+
+mode=n
+ The EFI stub will set the mode of the display to mode number n if
+ possible.
+
Edgar Hucek <gimli@dark-green.com>
diff --git a/drivers/firmware/efi/libstub/efi-stub-helper.c b/drivers/firmware/efi/libstub/efi-stub-helper.c
index 9f34c7242939..c6092b6038cf 100644
--- a/drivers/firmware/efi/libstub/efi-stub-helper.c
+++ b/drivers/firmware/efi/libstub/efi-stub-helper.c
@@ -105,6 +105,9 @@ efi_status_t efi_parse_options(char const *cmdline)
efi_disable_pci_dma = true;
if (parse_option_str(val, "no_disable_early_pci_dma"))
efi_disable_pci_dma = false;
+ } else if (!strcmp(param, "video") &&
+ val && strstarts(val, "efifb:")) {
+ efi_parse_option_graphics(val + strlen("efifb:"));
}
}
efi_bs_call(free_pool, buf);
diff --git a/drivers/firmware/efi/libstub/efistub.h b/drivers/firmware/efi/libstub/efistub.h
index 321244ed20a4..9af65be3b278 100644
--- a/drivers/firmware/efi/libstub/efistub.h
+++ b/drivers/firmware/efi/libstub/efistub.h
@@ -666,6 +666,8 @@ efi_status_t efi_relocate_kernel(unsigned long *image_addr,

efi_status_t efi_parse_options(char const *cmdline);

+void efi_parse_option_graphics(char *option);
+
efi_status_t efi_setup_gop(struct screen_info *si, efi_guid_t *proto,
unsigned long size);

diff --git a/drivers/firmware/efi/libstub/gop.c b/drivers/firmware/efi/libstub/gop.c
index 2d91699e3061..a32b784b4577 100644
--- a/drivers/firmware/efi/libstub/gop.c
+++ b/drivers/firmware/efi/libstub/gop.c
@@ -8,11 +8,115 @@
#include <linux/bitops.h>
#include <linux/efi.h>
#include <linux/screen_info.h>
+#include <linux/string.h>
#include <asm/efi.h>
#include <asm/setup.h>

#include "efistub.h"

+enum efi_cmdline_option {
+ EFI_CMDLINE_NONE,
+ EFI_CMDLINE_MODE_NUM,
+};
+
+static struct {
+ enum efi_cmdline_option option;
+ u32 mode;
+} cmdline __efistub_global = { .option = EFI_CMDLINE_NONE };
+
+static bool parse_modenum(char *option, char **next)
+{
+ u32 m;
+
+ if (!strstarts(option, "mode="))
+ return false;
+ option += strlen("mode=");
+ m = simple_strtoull(option, &option, 0);
+ if (*option && *option++ != ',')
+ return false;
+ cmdline.option = EFI_CMDLINE_MODE_NUM;
+ cmdline.mode = m;
+
+ *next = option;
+ return true;
+}
+
+void efi_parse_option_graphics(char *option)
+{
+ while (*option) {
+ if (parse_modenum(option, &option))
+ continue;
+
+ while (*option && *option++ != ',')
+ ;
+ }
+}
+
+static u32 choose_mode_modenum(efi_graphics_output_protocol_t *gop)
+{
+ efi_status_t status;
+
+ efi_graphics_output_protocol_mode_t *mode;
+ efi_graphics_output_mode_info_t *info;
+ unsigned long info_size;
+
+ u32 max_mode, cur_mode;
+ int pf;
+
+ mode = efi_table_attr(gop, mode);
+
+ cur_mode = efi_table_attr(mode, mode);
+ if (cmdline.mode == cur_mode)
+ return cur_mode;
+
+ max_mode = efi_table_attr(mode, max_mode);
+ if (cmdline.mode >= max_mode) {
+ efi_printk("Requested mode is invalid\n");
+ return cur_mode;
+ }
+
+ status = efi_call_proto(gop, query_mode, cmdline.mode,
+ &info_size, &info);
+ if (status != EFI_SUCCESS) {
+ efi_printk("Couldn't get mode information\n");
+ return cur_mode;
+ }
+
+ pf = info->pixel_format;
+
+ efi_bs_call(free_pool, info);
+
+ if (pf == PIXEL_BLT_ONLY || pf >= PIXEL_FORMAT_MAX) {
+ efi_printk("Invalid PixelFormat\n");
+ return cur_mode;
+ }
+
+ return cmdline.mode;
+}
+
+static void set_mode(efi_graphics_output_protocol_t *gop)
+{
+ efi_graphics_output_protocol_mode_t *mode;
+ u32 cur_mode, new_mode;
+
+ switch (cmdline.option) {
+ case EFI_CMDLINE_MODE_NUM:
+ new_mode = choose_mode_modenum(gop);
+ break;
+ default:
+ return;
+ }
+
+ mode = efi_table_attr(gop, mode);
+ cur_mode = efi_table_attr(mode, mode);
+
+ if (new_mode == cur_mode)
+ return;
+
+ if (efi_call_proto(gop, set_mode, new_mode) != EFI_SUCCESS)
+ efi_printk("Failed to set requested mode\n");
+}
+
static void find_bits(u32 mask, u8 *pos, u8 *size)
{
if (!mask) {
@@ -124,6 +228,9 @@ static efi_status_t setup_gop(struct screen_info *si, efi_guid_t *proto,
if (!gop)
return EFI_NOT_FOUND;

+ /* Change mode if requested */
+ set_mode(gop);
+
/* EFI framebuffer */
mode = efi_table_attr(gop, mode);
info = efi_table_attr(mode, info);
--
2.17.1